In electronic color imaging, it is desirable to simultaneously capture image data in three color planes, usually red, green and blue, although cyan, magenta, and yellow can also be used. When the three color planes are combined, it is possible to create high-quality color images. Capturing these three sets of image data can be done in a number of ways. In electronic photography, this is sometimes accomplished by using a single two dimensional array of sensors that are covered by a pattern of red, green and blue filters. This type of sensor is known as a color filter array or CFA. Below is shown the red (R), green (G) and blue (B) pixels as are commonly arranged on a CFA sensor.
When a color image is captured using a CFA, it is necessary to interpolate the red, green and blue values so that there is an estimate of all three color values for each sensor location. Once the interpolation is done, each picture element, or pixel, has three color values and can be processed by a variety of known image processing techniques depending on the needs of the system. Some examples of the reasons for processing are to do image sharpening, color correction or halftoning.
The following shows how red green and blue pixels can be arranged in a particular color filter array pattern, hereinafter referred to as the Bayer color filter array. For a more detailed description see U.S. Pat. No. 3,971,065 to Bayer. ##EQU1##
In processing color digital images produced by an image sensor, color specification values such as, for example, luminance and chrominance values for each pixel need to be computed. One of the problems found in processing color image values produced by an image sensor is that the luminance values for pixels on the edge of a feature of an image can be inaccurately interpolated.